Earphones (also known as earbuds or headphones) are widely used for listening to audio sources for recreation. An earphone contains a receiver (a small speaker) that is held close to the user's ear to convert electric signals into sound. Earphones can be connected to an audio source, such as an audio amplifier or a media player, which resides in stationary equipment (e.g., a CD or DVD player, a home theater, a personal computer, etc.), or in a portable device (e.g., a digital audio player, an MP3 player, a mobile phone, a personal digital assistant, etc.).
An earphone may be combined or integrated with a microphone to form a headset, that is used for two-way communications through a host device, such as a cellular phone, or a desktop or laptop computer executing voice over IP (Internet Protocol) software. The headset can communicate with the host device through either a wired connection or a wireless link.